The present invention relates to an automatic air balancer system for maintaining various kinds of load at a predetermined position and then moving the load at a desired speed, or outputting a desired mechanical force.
The present applicant filed an application with regard to an invention of an automatic air balancer system (prior invention, i.e., Japanese Patent Application Laid-Open (KOKAI) No. 5-238682), which includes: (a) a device for temporarily holding as an extension start voltage signal the pressure in a balance cylinder when a piston of the balance cylinder travels upward and enters the working range of a position detector; (b) a device for temporarily holding as a contraction start voltage signal the pressure in the balance cylinder when the balance cylinder piston travels downward and re-enters the working range of the position detector; (c) a device for outputting the extension start voltage signal and the contraction start voltage signal, which have been temporarily held, when the balance cylinder piston reaches a lower extremity position, and for obtaining a median of the difference between the extension start voltage signal and the contraction start voltage signal and then adding the contraction start voltage signal to the median; and (d) a device for using a value obtained as a result of the addition of the contraction start voltage signal to the median as a balance pressure signal for the balance cylinder.
It should be noted that the position detector has a distance between a position where the position detector is turned on by approach of the piston and a position where it is turned off by travel of the piston in the reverse direction during the next stroke. The distance is called "differential gap". At present, the differential gap is 2 mm or less in the case of a position detector with contacts and 1 mm or less in the case of a contactless position detector. In the prior invention, the position detector is disposed at a position where the position detector outputs an on-signal by detecting downward travel of the piston (i.e., the lower extremity position of the piston). When the piston travels upward (moves upward) and the travel distance exceeds the differential gap, the position detector outputs an off-signal.
The main purpose of the automatic air balancer system of the prior invention is to move various kinds of load up and down by the balance cylinder and to maintain the piston at a predetermined position by controlling the air pressure in the balance cylinder. Thus, the automatic air balancer system of the prior invention is incapable of moving various kinds of load vertically and horizontally at a desired speed, or applying a desired mechanical force to various kinds of object, and it has no security function that enables the piston to be surely kept suspended when the system is stopped.